The present invention relates to foam-in-place packaging and, more particularly, to a simplified and improved apparatus and process for producing foam-in-place packaging cushions and other flexible, fluid-filled containers.
Foam-in-place packaging is a highly useful technique for on-demand protection of packaged objects. In its most basic form, foam-in-place packaging comprises injecting foamable compositions from a dispenser into a container that holds an object to be cushioned. Typically, the object is wrapped in plastic to keep it from direct contact with the rising (expanding) foam. As the foam rises, it expands into the remaining space between the object and its container (e.g. a corrugated board box) thus forming a custom cushion for the object.
A common foamable composition is formed by mixing an isocyanate compound with a hydroxyl-containing material, such as a polyol (i.e., a compound that contains multiple hydroxyl groups), typically in the presence of water and a catalyst. The isocyanate and polyol precursors react to form polyurethane. At the same time, the water reacts with the isocyanate compound to produce carbon dioxide. The carbon dioxide causes the polyurethane to expand into a foamed cellular structure, i.e., a polyurethane foal', which serves to protect the packaged object.
In other types of foam-in-place packaging, an automated apparatus produces flexible bags or other containers from a flexible, plastic film web, and dispenses a foamable composition into the bags as the bags are being formed. As the composition expands into a foam within the bag, the bag is sealed shut and typically dropped into a container holding the object to be cushioned. The rising foam again tends to expand into the available space, but does so inside the bag. Because the bags are formed of flexible plastic, they form individual custom foam cushions around the packaged objects. Exemplary types of such packaging apparatus are assigned to the assignee of the present invention, and are illustrated, for example, in U.S. Pat. Nos. 4,800,708, 4,854,109, 5,027,583, 5,376,219, and 6,003,288, the contents of each of which are incorporated entirely herein by reference.
A variation of the foregoing ‘foam-in-bag’ method of creating packaging cushions is to segregate each cushion into one or more containers, which are filled with foamable composition and sealed closed. The foam-filled containers are generally elongated, i.e., tube-shaped, and are separated from adjacent containers by relatively flat regions of the film web, which provide bending regions or hinges for the cushion. While not providing custom-fitting cushions as with standard foam-in-place or foam-in-bag packaging techniques, foam-tube packaging cushions can generally be produced at a higher rate of speed than custom cushions, while still providing the ability to flexibly ensconce the packaged product due to the non-foamed hinge regions of the cushion. These attributes have been found to be advantageous for high-volume packaging applications.
At present, the foregoing foam-tube packaging technique is carried out by modifying conventional foam-in-bag packaging machines to form horizontally-oriented, foam-filled tubes within each packaging cushion. While such modifications have generally proven adequate, shortcomings exist. In the first place, the minimum width of the tubes is currently limited to about 2.5 inches. This is due, in part, to the placement of the foam dispensing apparatus substantially completely inside of the film web, which is conveyed in a vertical direction, with the tubes being horizontally aligned in order to accommodate the placement of the foam dispenser within the web. The spatial constraints of this arrangement do not permit a closer spacing of the transverse seals that form the tubes than about 2.5 inches. It would be desired to produce foam-tube packaging cushions with much smaller tube-widths, e.g., down to about 1 inch or less, which would enhance the flexibility and versatility of foam-tube packaging cushions, e.g., for packaging delicate objects or those having a relatively complex shape.
Additionally, the current foam-tube systems are intermittent, with the film web being stopped each time that a side wall for a tube is formed. Such side walls are created by producing transverse heat-seals, i.e., across the width of the film web, and occur in an alternating fashion with the dispensation of the foamable composition. Spacing between the transverse-seal/side-walls is dependent on the frequency of film-contact with the transverse seal mechanism which, in turn, is dependent on the control of the speed and stoppage of the film web. Such intermittent movement of the film web results in a slower process than would otherwise be desired for many, high-volume applications, in which a continuous/non-intermittent process would be preferred. In addition, control of the spacing of the transverse seals, and therefore of the width of the tubes, is limited. Further, intermittent dispensation of the foam makes it difficult to control both the volume of the foam dispensed into each tube, and also the mixing ratio of the foam precursor components, i.e., the polyol and isocyanate.
Accordingly, there is a need in the art for an improved apparatus for making foam-tube-type packaging cushions, which overcomes the foregoing shortcomings.